Alkylation of hydrocarbons



Jan'. 19, 1943.l F. MARsclimnEF"` ETAL 'f 2,308,562

-ALKYLATION OF HYDROCARBONS Filed March 31, 1942 Patented Jan. 19, 1943 ALKYLATION oF nYDRocAnnoNs Robert F. Marschner, Homewood, Ill., and Don R.

Carmody, Hammond, Ind., assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application March 31, 1942, Serial No. 437,050

' (ci. 19e-1o) 9 claims.

This invention relates to :theproduction of normally liquid hydrocarbons from normally gaseous hydrocarbons and relates more particu- Y larly to the alkylation of isoparafnic hydrocarbons-with olenic hydrocarbons in the presence of a catalyst.

For many years, it has been customary to subject petroleum hydrocarbons to cracking operations for the production of gasoline. One of the by-products from this operation is al varying amount of normally gaseousA hydrocarbons,

usually'comprising a mixture of ol'enic and parainic hydrocarbons in various proportions. These by-product' hydrocarbons were considered in the nature of waste gases until recent years when it has been realized that they are a valuable source of Iinitial stock for the production of definite hydrocarbons suitable either as aviation gasoline or as motor fuels of high octane number.

Various commercial operations have been proposed and employed for the conversion of the gaseous hydrocarbons to normally liquid hydrocarbons of gasoline boiling fange, including such processes as polymerization plus hydrogenation, alkylation, etc. The products from these processes have proved Aso valuable that various hydrocarbons'from other sources are now being diverted yfor conversion purposes, including gases from natural gas and from the light ends of products from distillate wells. Cracking, dehydrogenation and isomerization have been employed for the conversionof paraiiinic hydrocarbons to feed stocks suitable for these processes. Alkylation is perhaps a more desirable method of obtaining hydrocarbons suitable for butane (the only normally gaseous isoparailinic/ hydrocarbon) are also occasionally diverted to alkylation in order to obtain additional amounts of higher boiling hydrocarbons of high octane number. f

Itis an object of this invention to provide an improved process for the alkylation of isoparaflinic hydrocarbons, and more specically the alkylation of isobutane with normally gaseous oleflns to produce saturated branched-chain hydrocarbons within .the gasoline boiling range. Another object of our invention is to provide a process for the optimum conversion ofisoparafiinic hydrocarbons and olefins to branchedchain hydrocarbon` suitable for use as aviation fuels. An additioriarobject is to provide a process wherein isobutane is alkylated with ethylene' under conditions and with a; catalyst whereby the alkylation product is lobtained with a minimum of degradation to undesirable by-products.

It is also an object of our invention to provide an` improved process for the production of a high octane number gasoline meeting aviation gasoline specifications without blending with other hydrocarbon fractions. Other objects and advantages of our invention will become apparent as the description thereof proceeds.

In th'ey drawing:

Figure 1 is a plot depicting graphically the eiect of the ratio of bound" hydrocarbon to aluminum chloride in the catalyst on the rate of alkylation; and

Figure 2 is a plot depicting graphically the effect of the ratio of olefin reacted to isoparaflin present on the production of monoalkylate,

dialkylate and polyalkylates,

Briefly state, our invention contemplates the alkylation of an isoparailin such as Aisobutane with an olen such as ethylene in the presence of an particular catalyst comprising an aluminum halide-hydrocarbon complex under restricted conditions of temperature, pressure, and amount of activator in which the ratio of reactants is adjusted to yield a product of suitable boiling'range to meet aviation gasoline specications. y

Aluminum chloride has been employed for the alkylation, of isoparafflns by olefins, as well as numerous other hydrocarbon conversion processes, and it has been found by experiment that generally speaking, pure `aluminum chloride is too active tobe entirely satisfactory as a catalyst, i. e., the activity of the aluminum chloride as such is so great that numerous unwanted side reactions occur, such as polymerization, cracking,`isomerization, etc. Various methods have been proposed for modifying the catalytic activity of this compound. For example, very low temperatures can be employed such that cracking and polymerization are substantially avoided and the reaction'is primarily one of alkylation. Such temperatures, however, require much longer periods for .the reaction to become complete and therefore are neither advisable nor desirablecommercially. It has also been found that when reacting aluminum chloride with a normally liquid hydrocarbon, a complex or red oil is formed which is still catalytically active but in which the activity is considerably modified. The particular type of hydrocarbon with which the aluminum chloride reacts determines, to a marked degree, the type of complex which is formed, and complexes formed from the various types of hydrocarbons, such' as oleflns, straight-chain paraftlns, branched-chain parafiins, naphthenes or aromatics, differ considerably in their effectiveness in' promoting an olefin-paraflin alkylation reaction. Moreover,it has been proposed to form definite complexes between an aluminum halide and a hydrocarbon by employing such methods of synthesis as the Grignard reaction wherein the halogen of the aluminum halide is replaced by one or more hydrocarbon radicals. We have found that an aluminum halide-hydrocarbon complex prepared by the direct reaction of an aluminum halide with a saturated hydrocarbon is superior to the complexes formed by the reaction of the metal halide with other classes of hydrocarbons, and of the saturated hydrocarbons, the isoparafiinic hydrocarbons yield a complex of especially desirable activity.

The active liquid aluminum halide-hydrocarbon complex employed in our alkylation reaction is prepared by the action of an aluminum halide,

such as anhydrous aluminum chloride or aluminum bromide, and an activator comprising av hydrogen halide or a compound affording a hydrogen halide, on a substantially saturated fraction containing predominantly at least one paraflin hydrocarbon, preferably having at least two side chains. The reaction is carried out at a temperature in the range of from about F.- to about 175 F. .This liquid catalyst complex is suitably prepared from aluminum chloride and a substantially saturated fraction containing parafiln hydrocarbons having at least six total carbon atoms, and advantageously with at least two side chains per molecule. tions include, for example. the hydrogenated polymers and copolymers of olens having less than -six carbon atoms per molecule,V namely, ethylene, propylene and the butylenes and amylenes, and the products of alkylation of iso- 'butane and of is'opentane with such olens are particularly suitable. These -fractions are very rich in highly branched-paramnic hydrocarbons, `for example, ,isohexanea isolieptanes -or isooc- `tanes. We prefer-to prepare our complex froma fractin'ichin isooctanes, although fractions more volatile or less volatile but rich in branched- Such saturated frac-A chain hydrocarbons are also effective in producing the desired complex, and fractions containing substantially only linear paraillnic hydrocarbons are included.

As an example, an aluminum chloride-hydrocarbon complex was prepared by stirring togeth er at atmospheric pressure a quantity of anhydrous aluminum chloride with an excess of commercial isooctane and a minor amount of hydrogen chloride at -l20 F. to 140 F. until a liquid complex resulted. During the complex formation large amounts of isobutane ,were produced and the remaining hydrocarbon liquid contained a quantity of material of a higher boiling range than that present in the original isooctane. The viscosity of the complex catalyst thus produced was below 1000 seconds Saybolt viscosity at F. and the complex was easily pumpable. The complex contained approximately35% by weight of hydrocarbons. No complete and adequate analysis of the hydrocarbons joined to the aluminum chloride in the complex is known but investigations have shown that the hydrocarbons are not present in their original form, i. e., the isooctane is not joined to the aluminum chloride metathetically by the elimination, for example, of hydrogen'chloride. During the complex formation, thehydrocarbons are apparently converted to complicated ring structures with varying degrees of saturation and unsaturation. The analysis, of course, is unimportant except in so far as it serves to distinguish the complex from those formed, for example, by means of the Grignard reaction employing alkyl halides and magnesium.

Throughout the specification and claims whenever the term aluminum chloride-parafiinic hydrocarbon complex or paraiiinic complex is employed, itis intended to designate the liquid complex formed by the reaction of an aluminum 'halide with a paraiiinic hydrocarbon inaccordance with a procedure of the general type described above. We also refer to our complex as containingbound hydrocarbons. This is to designate that the hydrocarbon is j'oined to the aluminum halide by chemical means, and to distinguish it from such catalysts as those comprising a slurry or solution of an aluminum halide in a liquid hydrocarbon.

In carrying out our alkylation process, isobutane and ethylene, for example, are contacted with the catalyst so that there is an intimate mingling of the feed stocks andthe catalyst. This can be accomplished by adding the isobutane to the complex with vigorous stirring and introducing the ethylene into the mixture, or the isobutane and ethylene can be intimately contacted and the mixture injected into contact with the complex. Various mechanical expedients can be employed'for assuring intimate contact between the reactants and catalyst, such as y for example, mechanical stirrers, tubular reactors, packed towers, turbo mixers, jet injectors, etc. The process can be carried out batchwise or continuously, the'latter method being the most ratio ofreactants.

32%, and most desirably about 28% by weight of bound hydrocarbons. This can be done by.

adding powdered anhydrous aluminum chloride to the complex previously prepared, to yield a substance of definite over-all aluminum chlorideto-bound hydrocarbon ratio, and this complex of limited aluminum chloride-.to-bound hydrocarbon ratio constitutes our preferred catalyst. l

Figure 1 illustrates the effect of employing an aluminum chloride-isoparanic hydrocarbon complex having various amounts of bound hydrocarbon'in the complex as a catalyst in the alkylation of isobutane with ethylene, employing otherwise substantially identical conditions of temperature, pressure, amount of activator and The weight percent' of bound hydrocarbons in the catalyst is plotted along the abscissa, and the rate of alkylation along the ordinate. The rate of alkylation is drogen chloride and ethyl chloride are particularly desirable activators. The amount of hydroge'n halide should be 4% or less by weight, based upon the aluminum chloride or aluminum bromide in the complex, and may be as low as 0.5%.

We have found that the presence of hydrogen during the reaction slows the rate of alkylation and therefore hydrogen should preferably be excluded from the reaction.

Inorder to obtain optimum yields of alkylate per unit of time suitable for use as aviation fuels lwithout blending, it is necessary to use a rather critically controlled ratio of reactants. A viation fuels, in addition to the requirement for octane numbers of about 100, also must have certain distillation characteristics in order to be adequate Reid vapor pressure of 'l pounds is required. A

predominantly monoalkylate fraction (hexane) will not pass these specifications, nor on the other I hand can too much dialkylate and higher be expressed in terms of gallons -of alkylate produced per pound of aluminum chloride per hour. It is obvious from the graph that the rate is much greater when the. weight percent of bound hydrocarbon in the catalyst lies between about 23% and about 32% than it is for lower c or higher percentages of hydrocarbon, peak activity being found at about 28% hydrocarbons by weight. During the course of the alkylation reaction, additional amounts of vhydrocarbon are added or bound to the complex, and in order to maintain such a catalyst near peak activity, it is only necessary to add aluminum chloride when the bound hydrocarbon content approaches 30 carried out by adding the olenic feed stock at a rate of not less than two cubic feet of olefin Der pound of complex per hour, and preferably at a rate of from about live to about twenty cubic feet per pound of complex per hour to obtain the optimum conversion. At rates very much higher than this, and particularly at rates above'about fifty cubic feet of olen per pound of catalyst per hour, not only is there grave danger of the reactants passing through unchanged, but temperature *control` becomes much more diflicult. At rates below that set forth, the contact between olen and paraffin in the large volume of catalyst becomes more difficult, and polymerization may occur to an undesirable-extent. The type of apparatus employed will iniluence to-some extent the rate. of olen addition. If a wide, shallow.

tower or a' tubular reactor of large diameter is employed, then obviously some additional means for mixing must be employed in order to obtain adequate contact between the reactants andthe catalyst. Y

The alkylation is preferably carriedoutin the presence of an activator, employing for that purpose lninor amounts of a hydrogen halide, such as hydrogen chloride or hydrogen bromide, or al substance affording a hydrogen halide under the ation gasoline without the-necessity of adding outside stocks of definite characteristics ordinarily required for modifying the original alkylate characteristics. When using' up to about 0.6 mol of ethylene reacted per mol of isobutane present the product is predominantly and fairly uniform- 'ly monoalkylate. When using greater amounts of ethylene,higher boiling parailins, particularly fthe dialkylates, are formed. Figure 2 illustrates ted along the ordinate and the percent by volume yield of alkylate along the abscissa. It is apparv 'ent from Figure 2 that the yield of the various hydrocarbons changes appreciably with increased sible to obtain an aviation gasoline of desired characteristics directly from the alkylate.

Although alkylation will occur at temperatures within the range of from about 0 to about 212 F., or higher, we have found that it is highly demuch less desirable is greatly increased.

The pressure should be superatmospheric and, while it can include a range of from. about 30 pounds per square inch up to about 500 pounds per square inch, we prefer that itbe maintained below lq pounds per square inch, although .the exact pressure employed does not all'ect the alkylation reaction .to the same extent that certain of the other variables do. In all cases the pressure is sufficiently great to maintain the reactants in the liquid or dissolved phase under the conditions of temperature employed, and usuallyv reactionconditions such as an alkyl halide. Hyl an ethylene partial pressure of about 50 pounds per square inch is employed.

escasos ing conditions within our preferred range, is showninTableII.'

Table I illustrates the advantages of carrying Table H out an alkylation process for producing chietly R N L M N o P monoalkylate under the conditions herein set 5' m forth. Various runs show deviations from the Mols IWL preferred conditions, and the consequent loss of enggglcitgf eiiiclency either as regards yield, product distribution or reaction rate. In all cases the runs '73 0-80 '88 L04 were made using isobutane and ethylene as the 3 3 2 2 reactants, and employing an aluminum chloride- 59 56 53 4 isoparamnic hydrocarbon complex containing at 2g 22 2g a? least 23% by weight of bound hydrocarbon. .1o 11 is 1b Samples of some of the products were analyticall; Sp'dd'o" ly fractionated on a laboratory column having 129 127 132 132 an emciency of about A theoretical plates. Lg ig L45?, g gg.: Overhead cuts having substantially five, six, seven 268 262 265 274 Lesa "im 275 F and eight carbon -atoms per molecule, and a rem 372 382 395 406 o sidual cut containing hydrocarbons having nine 20 1%+5% E E 309 313 335 Nle "m 307 or more carbon atoms per molecule were taken.

Table I Preferred Run No. A B C D E F G H mso '[emperature IF 13(` 128 `85 48 48 205 112 105 80-150 Reactor pressure, pounds per square inch.-. 130 135 95 100 105 250 150 130 50-150 Weight rcentHCl based onAlCl3 3 3 4 4 4 4 8 l0 iol'lces Mols ct ylene reacted per mol isobutane i present 0.56 0.57 0.54 0.47 0.53 0.40 0.48 1.15 Rate oi production of total alkylste-lbs.

alk late/1b. catalyst/hr 3.8 4.7 25 0.4 0.4 44 1.1 a1 Weig t percent total: Alkylate based on eth lene reacted 255 235 250 302 262 214 weig :balance percent 10o 98 o9 95 101 91 Product distribution:

P um 1o s 1 45 2o 4 ci c7 76 34 54 4o 6 5 4 12 s 9 14 15 16 9 1o 2o c s s (1) s 21 I i Included in octancs.

Runs A, B and C are illustrative of operation under preferred conditions when producing chiefly monoalkylate, runs A and B differing chiefly in the rate of production, while run C was carried, out at a much lower temperature. Runs D and E were carried out at a temperature below our preferred range, and, illustrate admirably the effect of such deviation from preferred conditions, since although the amount of dialkylate formed is'increased, the yield is much smaller and the reaction rate very low. In run F the temperature was above the range desired and although it will be noted that the yield of alkylate based on ethylene was greatly increased, the', product distribution shows that considerable cracking, etc., took place, the volume of pentanes being greatly increased atthe expense of the 'more desirable alkylates.

Run G illustrates the effect of too g`reat an amount of activator, the yield of monoalkylate being reduced with the formation of large quantities of pentanes. In run H, the mol ratio of ethylene to isobutane has been increased to 1.15; consequently the yield of dlalkylate (octanes) and higher boiling hydrocarbons has greatly increased, with a consequent decreasejin monoalkylate. In the nal column of the table the preferred conditions are summarized. When more than one of the operating conditions falls outsideor these preferred ranges, deviation from the optimum becomes more pronounced and the yield of alkylate is correspondingly reduced, or the rate of conversion becomes uneconomically low.

To illustrate the effect of regulating the mol ratio of ethylene to isobutylene to produce an aviation gasoline, the results of alkylating isobutane 'with various amounts of ethylene, employ- From the above it will be seen that, in order to obtain a product which on distillation will have the sum of the 10 and 50% evaporation vpoints greater than 307 F., about 0.77 mol of ethylene to every mol of 'isobutane must be employed. The underlined figures show those outside the speciilcations. On the other hand, if the ethylene reacted is much greater than about 1.05 mois for every mol oi isobutane present, then the product will rail to meet the evaporated" speciication of less than 275 F. Obviously, if the specifications for aviation gasoline are modified. it is within the scope of our invention that the ratio of the reactants Ibe modified under our optimum conditions to provide for the production of greater or lesser amounts of diand polvalkylates.

One particular advantage of our process is the production oi' a superfuel of highly satisfactory octane number and volatility characteristics without the addition of isooctane from an Vout-- side source, as has been the custom in the past. Another advantage is that the product need not be specially processed as by fractionation, blending, etc.. except for an initial stabilization to eliminate light hydrocarbons, thereby eliminating the need for producing the hydrocarbon fractions for blending purposes, and also elimination of the physical equipment necessary for proper blending, etc.

Although ,we have described our process relative to the alkylation of isobutane with ethylene. it should be understood that this is by way of illustration and not by way of limitation, and that the use of other oleilnic hydrocarbons, such as propylene, the butylenes. etc. is contemplated,

as well as the use of other low-boiling isoparafv nic hydrocarbons such as isopentane or even isohexane.

This application is a continuation-in-part of our copending application, Serial No. 398,556,

. led June 18, 1941.

We claim:

1. A process for the production of aviation gasoline of high octane number and balanced volatility characteristics which comprises contacting a low boiling isoparainic hydrocarbon with a normally gaseous olen in the presence of an aluminum halide-parainic hydrocarbon complex having from about 23% to about 32% by weight of bound hydrocarbons, and a hydrogen halide under conditions of temperature and pressure adapted to promote the reaction of said isoparainic hydrocarbons with said olenic hydrocarbons, and maintaining a mol ratio of normally gaseous olefin reacted to isoparamn hydrocarbon present of at least about 0.77 whereby a mixture containing at least mono, and dialkylates is formed.

2. A process according to claim 1 in which said normally gaseous olen contains less than four carbon atoms per molecule. l

- 3. A process for the production of aviation gasoline of high octane number and balanced volatility characteristics which comprises, contacting a low boiling isoparafiinic hydrocarbon with a normally gaseous olen in the presence of an said aluminum halide-parafnic hydrocarbon complex is aluminum chloride-hydrocarbon complex and said hydrogen halide is hydrogen chloride.

5. A process for the production of aviation gasoline of highl octane number and balanced volatility characteristics which comprises contacting isobutane with ethylene in the precence of an aluminum halide-parailinic hydrocarbon complex having from about 23% to about 32% bound hydrocarbons and in the presence of a small amount of hydrogen halide at a temperature within the range from about 80 F. to about 150 F. in the liquid phase, and maintaining a mol ratio of ethylene reacted to isobutane present of at least about 0.77 whereby a mixture of at least mono-, diand polyalkylates is formed which boils within aviation gasoline specications.

6. A process according to claim 5- in which said hydrogen halide present is not more than 4% by weight of the aluminum halide present.

'7. A process according to claim 5 in which the mol ratio of ethylene reacted to isobutane present is not less than 0.77. I

8. A process according to claim 5 in which the mol ratio of ethylene reacted to isobutane present is within the range from about 0.77 to about 1.05. v

9. A process according to claim 5 in which the ratio of ethylene reacted to isobutane present is adjusted to yield a product in which the 10% evaporation point is less than 167'? F.,A the 50% evaporation pointless than 212 F., the 90% evaporation point less than 275 F. and the sum of the individual temperatures at the 10% and evaporation points is not less than 307 F.,

se en pounds.

ROBERT F. MARSCHNER. DON R. CARMODY. 

